Atomic layer deposition of barrier materials

ABSTRACT

Methods for processing substrate to deposit barrier layers of one or more material layers by atomic layer deposition are provided. In one aspect, a method is provided for processing a substrate including depositing a metal nitride barrier layer on at least a portion of a substrate surface by alternately introducing one or more pulses of a metal containing compound and one or more pulses of a nitrogen containing compound and depositing a metal barrier layer on at least a portion of the metal nitride barrier layer by alternately introducing one or more pulses of a metal containing compound and one or more pulses of a reductant. A soak process may be performed on the substrate surface before deposition of the metal nitride barrier layer and/or metal barrier layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/871,864 (APPM/007971), filed Jun. 18, 2004, which application claimsbenefit of U.S. Provisional Patent Application Ser. No. 60/479,426(APPM/007971), filed Jun. 18, 2003. Both of the aforementioned patentapplications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to a method formanufacturing integrated circuit devices. More particularly, embodimentsof the invention relate to forming metal interconnect structures usingone or more cyclical deposition processes.

2. Description of the Related Art

As the structure size of integrated circuit (IC) devices is scaled downto sub-quarter micron dimensions, electrical resistance and currentdensities have become an area for concern and improvement. Multilevelinterconnect technology provides the conductive paths throughout an ICdevice, and are formed in high aspect ratio features, includingcontacts, plugs, vias, lines, wires, and other features. A typicalprocess for forming an interconnect on a substrate includes depositingone or more layers, etching at least one of the layer(s) to form one ormore features, depositing a barrier layer in the feature(s) anddepositing one or more layers to fill the feature. Typically, a featureis formed within a dielectric material disposed between a lowerconductive layer and an upper conductive layer. The interconnect isformed within the feature to link the upper and lower conductive layers.Reliable formation of these interconnect features is important to theproduction of the circuits and continued effort to increase circuitdensity and quality on individual substrates and die.

Copper has recently become a choice metal for filling sub-micron highaspect ratio, interconnect features because copper and its alloys havelower resistivities than aluminum. However, copper diffuses more readilyinto surrounding materials and can alter the electronic devicecharacteristics of the adjacent layers and, for example, form aconductive path between layers, thereby reducing the reliability of theoverall circuit and may even result in device failure.

Barrier layers therefore, are deposited prior to copper metallization toprevent or impede the diffusion of copper atoms. Barrier layerstypically contain a metal such as tungsten, titanium, tantalum, andnitrides thereof, which all have a greater resistivity than copper. Todeposit a barrier layer within a feature, the barrier layer must bedeposited on the bottom of the feature as well as the sidewalls thereof.Therefore, the additional amount of the barrier layer on the bottom ofthe feature not only increases the overall resistance of the feature,but also forms an obstruction between higher and lower metalinterconnects of a multi-layered interconnect structure.

There is a need, therefore, for an improved method for forming metalinterconnect structures which minimizes the electrical resistance of theinterconnect.

SUMMARY OF THE INVENTION

A method is provided for depositing barrier layers on substrate surfaceusing one or more atomic layer deposition techniques. In one aspect, amethod is provided for processing a substrate including exposing thesubstrate to a soak process comprising a tungsten-containing compoundand depositing a tantalum barrier layer on the substrate by an atomiclayer deposition process, comprising exposing the substrate tosequential pulses of a tantalum precursor and a reductant.

In another aspect, a method is provided for processing a substrateincluding depositing a tantalum nitride barrier layer on the substrateby an atomic layer deposition process, comprising exposing the substrateto sequential pulses of a first tantalum precursor and a nitrogenprecursor, exposing the substrate to a soak process comprising atungsten-containing compound, and depositing a tantalum barrier layer onthe tantalum nitride barrier layer by a second atomic layer depositionprocess, comprising exposing the substrate to sequential pulses of asecond tantalum precursor and a reductant.

In another aspect, a method is provided for processing a substrateincluding depositing a metal nitride layer on at least a portion of asubstrate surface by alternately introducing one or more pulses of afirst metal containing compound and one or more pulses of a nitrogencontaining compound, exposing the metal nitride layer to a firstnitrogen free reductant, exposing the metal nitride layer to a tungstencontaining compound, and depositing a metal containing barrier layer onat least a portion of the metal nitride layer by alternately introducingone or more pulses of a second metal containing compound and one or morepulses of a second nitrogen free reductant.

In another aspect, a method is provided for processing a substrateincluding depositing a tantalum nitride barrier layer on a substratesurface by alternately introducing one or more pulses of a firsttantalum containing compound and one or more pulses of a nitrogencontaining compound into a processing chamber, depositing a tantalumcontaining barrier layer on at least a portion of the tantalum nitridebarrier layer by alternately introducing one or more pulses of a secondtantalum containing compound and one or more pulses of a reductant intoa processing chamber, and exposing the tantalum containing barrier layerto a plasma treatment process.

In another aspect, a method is provided for processing a substrateincluding exposing the substrate to a first soak process, wherein thesoak process includes a first reductant for a predetermined time,depositing a tantalum nitride barrier layer on the substrate by anatomic layer deposition process in a process chamber, comprisingexposing the substrate to a first tantalum precursor, purging theprocess chamber with a purge gas, exposing the substrate with a nitrogenprecursor, and purging the process chamber with the purge gas, exposingthe substrate to a second soak process, and depositing a tantalumbarrier layer on the tantalum nitride barrier layer.

In another aspect, a method is provided for processing a substrateincluding depositing a tantalum nitride barrier layer on the substrateby an atomic layer deposition process in a process chamber includingexposing the substrate to a tantalum precursor, purging the processchamber with a purge gas, exposing the substrate to a nitrogenprecursor, and purging the process chamber with the purge gas, exposingthe substrate to a soak process, and depositing a tantalum barrier layeron the tantalum nitride barrier layer by a second atomic layerdeposition process including exposing the substrate to a second tantalumprecursor, purging with the purge gas, exposing the substrate with anitrogen free reductant, and purging with the purge gas.

In another aspect, a method is provided for processing a substrateincluding depositing a tantalum nitride barrier layer on the substrateby an atomic layer deposition process in a process chamber includingexposing the substrate to an organometallic tantalum precursor, purgingthe process chamber with a purge gas, exposing the substrate to anitrogen precursor, and purging the process chamber with the purge gas,and depositing a tantalum barrier layer on the tantalum nitride barrierlayer by a second atomic layer deposition process, comprising exposingthe substrate to sequential pulses of a tantalum halide precursor and areductant.

In another aspect, a method is provided for processing a substrateincluding depositing a nitride layer containing a first metal by a firstatomic layer deposition process, exposing the nitride layer to a soakprocess comprising a second metal different than the first metal, anddepositing a metal layer on the nitride layer by a second atomic layerdeposition process, wherein the metal layer comprises the first metal.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention are attained and can be understood in detail, a moreparticular description of the invention, briefly summarized above, maybe had by reference to the embodiments thereof which are illustrated inthe appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 illustrates a schematic plan view of an exemplary integratedcluster tool adaptable to perform the interconnect fabrication sequencedescribed herein;

FIG. 2 illustrates a schematic, partial cross section of one embodimentof an exemplary processing chamber for performing a cyclical depositiontechnique described herein;

FIG. 3 illustrates processing sequences according to various embodimentsof the invention described herein; and

FIGS. 4A-4D are schematic cross section views of an exemplary wafer atdifferent stages of an interconnect fabrication sequence according toembodiments described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A process sequence for forming one or more interconnect structures isprovided. Interconnect structures formed according to embodimentsdescribed herein have an overall lower resistivity and better electricalproperties than interconnects of the prior art, and are particularlyuseful for making memory and logic structures for use with thefabrication of integrated circuits. The formation of the interconnectstructures includes the formation of a barrier layer at least partiallydeposited on an underlying metal layer, a seed layer at least partiallydeposited on the barrier layer, and a bulk metal layer at leastpartially deposited on the seed layer.

The words and phrases used herein should be given their ordinary andcustomary meaning in the art by one skilled in the art unless otherwisefurther defined.

A “substrate surface” or “atomic layer deposition”, as used herein,refers to any substrate or material surface formed on a substrate uponwhich film processing is performed. For example, a substrate surface onwhich processing can be performed include materials such as silicon,silicon oxide, strained silicon, silicon on insulator (SOI), carbondoped silicon oxides, silicon nitride, doped silicon, germanium, galliumarsenide, glass, sapphire, and any other materials such as metals, metalnitrides, metal alloys, and other conductive materials, depending on theapplication. Barrier layers, metals or metal nitrides on a substratesurface include titanium, titanium nitride, tungsten nitride, tantalumand tantalum nitride. Substrates may have various dimensions, such as200 mm or 300 mm diameter wafers, as well as, rectangular or squarepanes. Embodiments of the processes described herein deposithafnium-containing compounds on many substrates and surfaces. Substrateson which embodiments of the invention may be useful include, but are notlimited to semiconductor wafers, such as crystalline silicon (e.g.,Si<100> or Si<111>), silicon oxide, strained silicon, SOI, silicongermanium, doped or undoped polysilicon, doped or undoped silicon waferssilicon nitride and patterned or non-patterned wafers. Surfaces includebare silicon wafers, films, layers and materials with dielectric,conductive and barrier properties and include aluminum oxide andpolysilicon. Pretreatment of surfaces includes polishing, etching,reduction, oxidation, hydroxylation, annealing and baking.

The term “interconnect” as used herein refers to any conductive pathformed within an integrated circuit. The term “bulk” as used hereinrefers to a greater amount of material deposited in relation to othermaterials deposited to form the interconnect structure. A “compound” isintended to include one or more precursors, reductants (reductants),reactants, and catalysts. Each compound may be a single compound or amixture/combination of two or more compounds.

“Atomic layer deposition” or “cyclical deposition” as used herein refersto the sequential introduction of two or more reactive compounds todeposit a layer of material on a substrate surface. The two, three ormore reactive compounds may alternatively be introduced into a reactionzone of a processing chamber. Usually, each reactive compound isseparated by a time delay to allow each compound to adhere and/or reacton the substrate surface. In one aspect, a first precursor or compound Ais pulsed into the reaction zone followed by a first time delay. Next, asecond precursor or compound B is pulsed into the reaction zone followedby a second delay. During each time delay a purge gas, such as nitrogen,is introduced into the processing chamber to purge the reaction zone orotherwise remove any residual reactive compound or by-products from thereaction zone. Alternatively, the purge gas may flow continuouslythroughout the deposition process so that only the purge gas flowsduring the time delay between pulses of reactive compounds. The reactivecompounds are alternatively pulsed until a desired film or filmthickness is formed on the substrate surface. In either scenario, theALD process of pulsing compound A, purge gas, pulsing compound B andpurge gas is a cycle. A cycle can start with either compound A orcompound B and continue the respective order of the cycle untilachieving a film with the desired thickness.

The term “inert gas” and “non-reactive gas” as used herein refers to asingle gas or a mixture of gases that does not participate in the metallayer formation. Exemplary non-reactive gases include argon, helium,nitrogen, and combinations thereof.

A “pulse”, “dose”, or “pulse/dose” as used herein is intended to referto a quantity of a particular compound that is intermittently ornon-continuously introduced into a reaction zone of a processingchamber. The quantity of a particular compound within each pulse mayvary over time, depending on the duration of the pulse. The duration ofeach pulse is variable depending upon a number of factors such as, forexample, the volume capacity of the process chamber employed, the vacuumsystem coupled thereto, and the volatility/reactivity of the particularcompound itself. A “half-reaction” as used herein is intended to referto a pulse of precursor step followed by a purge step. A pulse generallyhas a duration of less than about 1 second.

A “cycle” as used herein is intended to refer to two or more pulses ofdifferent particular compounds that are sequentially introduced into areaction zone. The quantity of a particular compound within each pulsemay vary over time, depending on the duration of the pulse. Cycles aretypically repeated for a deposition process.

A “soak” or “soak process” as used herein is intended to refer to aquantity of a particular compound that is introduced into a reactionzone of a processing chamber to activate a surface of a substrate. Theactivation of the surface may comprise hydrating a surface, catalyzing asurface, or forming halide terminated surfaces. A particular soakprocess may include a single compound or a mixture/combination of two ormore compounds. A soak only comprise one cycle if two or more compoundsare used. Soak processes generally have durations of about 1 second ormore.

A “reaction zone” is intended to include any volume that is in fluidcommunication with a substrate surface being processed. The reactionzone may include any volume within a processing chamber that is betweena gas source and the substrate surface. For example, the reaction zoneincludes any volume downstream of a dosing valve in which a substrate isdisposed.

Deposition Apparatus

FIG. 1 is a schematic top-view diagram of an exemplary multi-chamberprocessing system 100 that may be adapted to perform processes asdisclosed herein. Such a processing system 100 may be an ENDURA® system,commercially available from Applied Materials, Inc., of Santa Clara,Calif. A similar multi-chamber processing system is disclosed in U.S.Pat. No. 5,186,718, entitled “Stage Vacuum Wafer Processing System andMethod,” issued on Feb. 16, 1993, which is incorporated by referenceherein.

The system 100 generally includes load lock chambers 102, 104 for thetransfer of substrates into and out from the system 100. Typically,since the system 100 is under vacuum, the load lock chambers 102, 104may “pump down” the substrates introduced into the system 100. A firstrobot 410 may transfer the substrates between the load lock chambers102, 104, and a first set of one or more substrate processing chambers112, 114, 116, 118 (four are shown). Each processing chamber 112, 114,116, 118, can be outfitted to perform a number of substrate processingoperations such as cyclical layer deposition, chemical vapor deposition(CVD), physical vapor deposition (PVD), etch, pre-clean, degas,orientation and other substrate processes. The first robot 110 alsotransfers substrates to/from one or more transfer chambers 122, 124.

The transfer chambers 122, 124, are used to maintain ultrahigh vacuumconditions while allowing substrates to be transferred within the system100. A second robot 130 may transfer the substrates between the transferchambers 122, 124 and a second set of one or more processing chambers132, 134, 136, and 138. Similar to processing chambers 112, 114, 116,118, the processing chambers 132, 134, 136, 138 can be outfitted toperform a variety of substrate processing operations, such as cyclicallayer deposition, chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, and orientation, for example.Any of the substrate processing chambers 112, 114, 116, 118, 132, 134,136, 138 may be removed from the system 100 if not necessary for aparticular process to be performed by the system 100.

In one arrangement, each processing chamber 132 and 138 may be aphysical vapor deposition chamber, a chemical vapor deposition chamber,or a cyclical deposition chamber adapted to deposit a seed layer. Eachprocessing chamber 134 and 136 may be a cyclical deposition chamber, achemical vapor deposition chamber, or a physical vapor depositionchamber adapted to deposit a barrier layer. Each processing chamber 112and 114 may be a physical vapor deposition chamber, a chemical vapordeposition chamber, or a cyclical deposition chamber adapted to deposita dielectric layer. Each processing chamber 116 and 118 may be an etchchamber outfitted to etch apertures or openings for interconnectfeatures. This one particular arrangement of the system 100 is providedto illustrate the invention and should not be used to limit the scope ofthe invention.

To facilitate the control and automation of the overall system, theintegrated processing system may include a controller 140 comprising acentral processing unit (CPU), memory, and support circuits. The CPU maybe one of any form of computer processors that are used in industrialsettings for controlling various drives and pressures. The memory isconnected to the CPU, and may be one or more of a readily availablememory such as random access memory (RAM), read only memory (ROM),floppy disk, hard disk, or any other form of digital storage, local orremote. Software instructions and data can be coded and stored withinthe memory for instructing the CPU. The support circuits are alsoconnected to the CPU for supporting the processor in a conventionalmanner. The support circuits may include cache, power supplies, clockcircuits, input/output circuitry, subsystems, and the like.

FIG. 2 illustrates a schematic, partial cross section of an exemplaryprocessing chamber 200 for forming a barrier layer according toembodiments of the present invention. Such a processing chamber 200 isavailable from Applied Materials, Inc. located in Santa Clara, Calif.,and a brief description thereof follows. A more detailed description maybe found in commonly assigned U.S. patent application Ser. No.10/032,284, entitled “Gas Delivery Apparatus and Method For Atomic LayerDeposition”, filed on Dec. 21, 2001, which is incorporated herein byreference to the extent not inconsistent with the claimed aspects anddisclosure herein.

The processing chamber 200 may be integrated into an integratedprocessing platform, such as an ENDURA® platform also available fromApplied Materials, Inc. Details of the ENDURA® platform are described incommonly assigned U.S. patent application Ser. No. 09/451,628, entitled“Integrated Modular Processing Platform”, filed on Nov. 30, 1999, whichis incorporated herein by reference to the extent not inconsistent withthe claimed aspects and disclosure herein.

Referring to FIG. 2, the chamber 200 includes a chamber body 202 havinga slit valve 208 formed in a sidewall 204 thereof and a substratesupport 212 disposed therein. The substrate support 212 is mounted to alift motor 214 to raise and lower the substrate support 212 and asubstrate 210 disposed thereon. The substrate support 212 may alsoinclude a vacuum chuck, an electrostatic chuck, or a clamp ring forsecuring the substrate 212 to the substrate support 212 duringprocessing. Further, the substrate support 212 may be heated using anembedded heating element, such as a resistive heater, or may be heatedusing radiant heat, such as heating lamps disposed above the substratesupport 212. A purge ring 222 may be disposed on the substrate support212 to define a purge channel 224 that provides a purge gas to preventdeposition on a peripheral portion of the substrate 210.

A gas delivery apparatus 230 is disposed at an upper portion of thechamber body 202 to provide a gas, such as a process gas and/or a purgegas, to the chamber 200. A vacuum system 278 is in communication with apumping channel 279 to evacuate gases from the chamber 200 and to helpmaintain a desired pressure or a desired pressure range inside a pumpingzone 266 of the chamber 200.

The gas delivery apparatus 230 includes a chamber lid 232 having anexpanding channel 234 formed within a central portion thereof. Thechamber lid 232 also includes a bottom surface 260 extending from theexpanding channel 234 to a peripheral portion of the chamber lid 232.The bottom surface 260 is sized and shaped to substantially cover thesubstrate 210 disposed on the substrate support 212. The expandingchannel 234 has an inner diameter that gradually increases from an upperportion 237 to a lower portion 235 adjacent the bottom surface 260 ofthe chamber lid 232. The velocity of a gas flowing therethroughdecreases as the gas flows through the expanding channel 234 due to theexpansion of the gas. The decreased gas velocity reduces the likelihoodof blowing off reactants adsorbed on the surface of the substrate 210.

The gas delivery apparatus 230 also includes at least two high speedactuating valves 242 having one or more ports. At least one valve 242 isdedicated to each reactive compound. For example, a first valve isdedicated to a metal containing compound, such as tantalum and titanium,and a second valve is dedicated to a nitrogen containing compound. Whena ternary material is desired, a third valve is dedicated to anadditional compound. For example, if a silicide is desired, theadditional compound may be a silicon containing compound.

The valves 242 may be any valve capable of precisely and repeatedlydelivering short pulses of compounds into the chamber body 202. In somecases, the on/off cycles or pulses of the valves 242 may be as fast asabout 100 msec or less. The valves 242 can be directly controlled by asystem computer, such as a mainframe for example, or controlled by achamber/application specific controller, such as a programmable logiccomputer (PLC) which is described in more detail in the assigned U.S.Pat. No. 6,734,020, entitled “Valve Control System For ALD Chamber”,issued on May 11, 2004, which is incorporated herein by reference to theextent not inconsistent with the claimed aspects and disclosure herein.For example, the valves 242 may be electronically controlled (EC)valves, which are commercially available from Fujikin of Japan as partnumber FR-21-6.35 UGF-APD.

Returning to FIG. 1, a control unit 280, such as a programmed personalcomputer, work station computer, or the like, may be coupled to thechamber 200 to control processing conditions. For example, the controlunit 280 may be configured to control flow of various process gases andpurge gases from gas sources 238, 239, 240 through the valves 242A, 242Bduring different stages of a substrate process sequence. The controlunit 280 may be one of any form of general purpose computer processorthat can be used in an industrial setting for controlling variouschambers and sub-processors.

Illustratively, the control unit 280 comprises a central processing unit(CPU), support circuitry, and memory containing associated controlsoftware. The CPU may use any suitable memory, such as random accessmemory, read only memory, floppy disk drive, hard disk, or any otherform of digital storage, local or remote. Various support circuits maybe coupled to the CPU for supporting the chamber 200. The control unit280 may be coupled to another controller that is located adjacentindividual chamber components, such as the programmable logiccontrollers of the valves 242A, 242B. Bi-directional communicationsbetween the control unit 280 and various other components of the chamber200 are handled through numerous signal cables collectively referred toas signal buses. In addition to control of process gases and purge gasesfrom gas sources 238, 239, 240 and from the programmable logiccontrollers of the valves 242A, 242B, the control unit 280 may beconfigured to be responsible for automated control of other activitiesused in wafer processing, such as wafer transport, temperature control,chamber evacuation, among other activities, some of which are describedelsewhere herein.

Barrier Deposition Process

FIGS. 3 and 4A-4D illustrate one embodiment of a process sequence 300according to embodiments of the invention. A substrate 410 is providedwith a patterned dielectric layer 412 disposed thereon at step 310 asshown in FIG. 4A. A feature definition 414 is formed in the patterneddielectric material 412. The feature definition 414 has sidewall 416 anda bottom 418. The substrate 410 may have features 407 formed therein,for example, underlying metal gates or metal interconnects. An optionalpre-treatment process, such as forming an initiation layer or a surfacetreatment process, such as a “soak” process, may be performed at step315 prior to deposition.

A metal nitride barrier layer 430 is first deposited at least partiallywithin the feature definition 414 and on the substrate surface, as shownat step 320 and FIG. 4B. The metal nitride barrier layer 430 isdeposited as atomic layers according to a cyclical layer depositiontechnique described herein. In one aspect, the barrier layer is a metalnitride material, such as tantalum nitride (TaN). Examples of othersuitable metal nitride material include tantalum silicon nitride,titanium nitride, titanium silicon nitride, tungsten nitride, tungstensilicon nitride, niobium nitride, molybdenum nitride, alloys thereof,and combinations thereof, among others. A soak process may also beperformed during an intermediate portion of the deposition process ofthe metal nitride barrier layer 430.

Optionally, the metal nitride barrier layer 430 may then be treated witha post-treatment process, such as a reducing gas plasma (or reductant asdescribed herein) to remove impurities and contaminants. An optionalpre-treatment process or a surface treatment process, such as a “soak”process, may be performed at step 325 prior to deposition of the metalbarrier layer 440.

A metal barrier layer 440 may then be deposited on the metal nitridebarrier layer 430, as shown at step 330 and FIG. 4C. The metal barrierlayer 440 is deposited according to a cyclical layer depositiontechnique described herein. In one aspect, the metal barrier layer 440is a metal containing layer, for example, tantalum, tantalum silicide,tantalum boride, titanium, titanium silicide, titanium boride, tungsten,tungsten silicide, tungsten boride, niobium, niobium silicide, niobiumboride, molybdenum, molybdenum silicide, molybdenum boride, ruthenium,ruthenium boride, ruthenium silicide alloys thereof, and combinationsthereof. A soak process may also be performed during an intermediateportion of the deposition process of the metal barrier layer 440.

The metal barrier layer 440 may then be treated with a post-treatmentprocess, such as a reducing gas plasma, to remove impurities andcontaminants at step 340. The layer 430 and 440 may also be used as awetting layer, adhesion layer, or glue layer for subsequentmetallization. An optional pre-treatment process, such as forming aninitiation layer during a “soak” process, may be performed before orduring an intermediate portion of the metal barrier layer 440 depositionprocess. The metal nitride barrier layer 430 and metal barrier layer 440may be deposited in the same chamber, in separate chambers, transferchamber, or system without breaking vacuum.

Alternatively, a barrier enhancement layer may be deposited on the metalnitride barrier layer 430 or metal barrier layer 440.

A seed layer 450 is at least partially deposited on the barrier layers430, 440, at step 350 as shown in FIG. 4D. The seed layer 450 may bedeposited using any conventional deposition technique, such as chemicalvapor deposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), electroplating, or electroless plating. Preferably,the seed layer 450 is deposited conformally on the underlying barrierlayers 430, 440. The seed layer 450 may be a conventional copper seedlayer or dual alloy seed layer. Exemplary dual alloy seed layersinclude: 1) undoped copper deposited utilizing a target containingundoped copper, 2) a copper alloy containing aluminum in a concentrationof about 2.0 atomic percent deposited utilizing a copper-aluminum targetcomprising aluminum in a concentration of about 2.0 atomic percent, 3) acopper alloy containing tin in a concentration of about 2.0 atomicpercent deposited utilizing a copper-tin target comprising tin in aconcentration of about 2.0 atomic percent, and 4) a copper alloycontaining zirconium in a concentration of about 2.0 atomic percentdeposited utilizing a copper-zirconium target comprising zirconium in aconcentration of about 2.0 atomic percent.

The bulk metal layer 460 is at least partially deposited on the seedlayer 450, at step 360 as shown in FIG. 4D. The metal layer may also bedeposited using any conventional deposition technique, such as chemicalvapor deposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), electroplating, or electroless plating. The metallayer preferably includes any conductive material such as aluminum,copper, tungsten, alloys thereof, or combinations thereof, for example.

Referring to FIG. 4A, the dielectric layer 412 may be any dielectricmaterial including a low k dielectric material (k≦4.0), whetherpresently known or yet to be discovered. For example, the dielectriclayer 412 may be a silicon oxide or a carbon doped silicon oxide, forexample. The dielectric layer 412 has been etched to form a featuredefinition 414 therein using conventional and well-known techniques. Thefeature definition 414 may be a plug, via, contact, line, wire, or anyother interconnect component. Typically, the feature definition 414 hasvertical sidewalls 416 and a floor 418, having an aspect ratio of about4:1 or greater, such as about 6:1. The floor 418 exposes at least aportion of the lower level metal interconnect 410.

Pre-Deposition Techniques

Prior to depositing the metal nitride barrier layer 430 or the metallayer 440, the patterned or etched substrate dielectric layer 412 may becleaned to remove native oxides or other contaminants from the surfacethereof. For example, reactive gases are excited into a plasma within aremote plasma source chamber such as a Reactive Pre-clean chamberavailable from Applied Materials, Inc., located in Santa Clara, Calif.Pre-cleaning may also be done within a metal CVD or PVD chamber byconnecting the remote plasma source thereto. Alternatively, metaldeposition chambers having gas delivery systems could be modified todeliver the pre-cleaning gas plasma through existing gas inlets such asa gas distribution showerhead positioned above the substrate.

In one aspect, the reactive pre-clean process forms radicals from aplasma of one or more inert gases such as argon, nitrogen, and heliumand/or one or more reactive gases including hydrogen, oxygen, andfluorine containing compounds, and combinations thereof. For example, aprocessing gas may include a mixture of tetrafluorocarbon (CF₄) andoxygen (O₂), or a mixture of helium (He) and nitrogen trifluoride (NF₃).More preferably, the reactive gas is a mixture of helium and nitrogentrifluoride.

In one example of a pre-clean process, a substrate is first exposed to aplasma of an inert gas, such as argon, and then chamber pressure isprovided to about 140 milliTorr, and a processing gas consistingessentially of hydrogen and helium is introduced into the processingregion. Preferably, the processing gas comprises about 5% hydrogen andabout 95% helium. The hydrogen plasma is generated by applying betweenabout 50 watts and about 1,000 watts power. The hydrogen plasma ismaintained for about 10 seconds to about 300 seconds.

Prior to deposition of the barrier layers 430 or 440, the substratesurface may be exposed to surface treatment process, a “soak” process,to enhance deposition of subsequent materials, such as to improve metaland/or metal nitride deposition. The substrate surface may include adielectric material, a conductive material, such as a metal, or acombination of both materials.

A soak process may be performed by exposing the substrate surface to aprocessing gas. A soak process may be applied by exposing the substratesurface to a reductant, as described herein, without pulsing. Soakprocesses differ from atomic layer deposition process by usuallyoccurring for only one cycle for two component soak processes and occurfor a duration of 1 or more seconds, such as between about 5 seconds andabout 330 seconds, for example 60 seconds. A plasma may also be used incombination with the soak process. Suitable reductants include hydrogen,borane and borane derivatives such as diborane (B₂H₆), triborane,tetraborane, pentaborane, hexaborane, heptaborane, octaborane,nanoborane, decaborane, alkylboranes (e.g., Et₃B), and combinationsthereof, silane and silane derivatives such as tetrachlorosilane(SiCl₄), disilane (Si₂H₆), hexachlorodisilane (Si₂Cl₆) or dichlorosilane(SiCl₂H₂), a gas having one or more amine groups disposed thereon, suchas ammonia or hydrazine (N₂H₄), and combinations thereof.

For example, for a metal nitride deposition process, which may also beused for metal deposition process, a soak of the substrate surface maybe performed by exposing the substrate surface to a processing gascapable of forming amine groups on the substrate surface. Exampleprocessing gas may include ammonia, a gas mixture comprising nitrogenand hydrogen, ammonia, hydrazine, methylhydrazine, dimethylhydrazine,t-butylhydrazine, phenylhydrazine, azoisobutane, ethylazide, derivativesthereof, and combinations thereof.

A soak process may also include a metal precursor soak usedindependently or in conjunction with a reductant described herein. Forexample, a soak process with a metal precursor may be used to halogenatea substrate surface for metal deposition. Halogenation of a substratesurface by a soak process may be achieved by metal halide soaksincluding halides of tantalum, titanium, tungsten, hafnium, zirconium,molybdenum, niobium, vanadium, ruthenium, and aluminum, as well asnon-metal halide compounds, such as silicon, germanium and carbon.Examples of metal halide compounds include TaF₅, TaCl₅, WF₆, TiCl₄,HfCl₄, ZrCl₄, AlCl₃ and MoCl₆.

It is believed the soak process may activate a substrate surface byhydrating or halogenating the substrate surface, and may even form alayer of deposited material, known as an initiation layer or soak layer.The soak process is selective by desired termination of the underlayerand dependant to what chemical reagent will start the ALD cycle. Thecompounds used in the soak process allow the formation of a surface ofdeposition with desired chemical structure. For example, if the ALDcycle starts with a reductant (e.g., B₂H₆ or SiH₄), then a halogenatedterminus underlayer is desired, so a metal halide compound is used inthe soak process. However, if the ALD cycle starts with a metalprecursor (e.g., TaF₅), then a hydrogenated terminus underlayer isdesired, so a reductant is used in the soak process.

For example, the use of a silane or borane compound with produce ahydrogen terminated surface to facilitate subsequent materialdeposition, an ammonia compound with produce an amine terminated surfacefacilitate subsequent material deposition, and the use of precursorsincluding halide compounds, such as TaF₅ or WF₆, can produce a fluorineterminated surface facilitate subsequent material deposition. The soakprocess is believed to facilitate the growth process of a subsequentatomic layer deposition process or chemical vapor deposition process.

An example of a soak process includes exposing a substrate surface toammonia between about 1 second and about 120 seconds, for example 60seconds, without pulsing, such as between about 5 seconds and about 60seconds, for example, between about 10 seconds and about 30 seconds.

The soak process may include two or more steps using two or morereductants. Additionally, the soak process may also include metalcontaining compounds, such as precursor used to deposit the metal ormetal nitride materials described herein. In one embodiment of atwo-step soak process, a reductant soak is followed by a precursor soak.For example, a metal containing compound (precursor) soak, such as TaF₅or WF₆, may be performed after the reductant soak described herein priorto depositing the metal nitride layer 430 or metal layer 440 asdescribed herein. In another embodiment, the reductant soak may beperformed after the metal containing compound soak, for example, a soakof WF₆ followed by a soak of diborane or silane. Each soak step of atwo-step soak process may be performed between about 5 seconds and about330 seconds as described herein.

Examples of two step soak processes may also include a reductant soakfollowed by a metal precursor soak, for example, a soak process mayinclude a 5 second B₂H₆ soak followed by a 300 second TaF₅ soak; anothersoak process may include a 10 second B₂H₆ followed by a 300 second TaF₅soak; another soak process may include a 20 second B₂H₆ followed by a300 second TaF₅ soak; another soak process may include a 20 second B₂H₆followed by a 30 second TaF₅ soak; another soak process may include a 20second B₂H₆ followed by a 100 second TaF₅ soak; and another soak processmay include a 20 second B₂H₆ followed by a 200 second TaF₅ soak. Inanother example of a two step soak process, a soak process may include a5 second SiH₄ soak followed by a 300 second TaF₅ soak; another soakprocess may include a 10 second SiH₄ followed by a 300 second TaF₅ soak;another soak process may include a 20 second SiH₄ followed by a 300second TaF₅ soak; another soak process may include a 20 second SiH₄followed by a 30 second TaF₅ soak; another soak process may include a 20second SiH₄ followed by a 100 second TaF₅ soak; and another soak processmay include and 20 second B₂H₆ followed by a 200 second TaF₅ soak.

Other examples of soak processes include a 5 second B₂H₆ soak followedby a 300 second WF₆ soak; another soak process may include a 10 secondB₂H₆ followed by a 300 second WF₆ soak; another soak process may includea 20 second B₂H₆ followed by a 300 second WF₆ soak; another soak processmay include a 20 second B₂H₆ followed by a 30 second WF₆ soak; anothersoak process may include a 20 second B₂H₆ followed by a 100 second WF₆soak; and another soak process may include a 20 second B₂H₆ followed bya 200 second WF₆ soak. In another example of a two step soak process, asoak process may include a 5 second SiH₄ soak followed by a 300 secondWF₆ soak; another soak process may include a 10 second SiH₄ followed bya 300 second WF₆ soak; another soak process may include a 20 second SiH₄followed by a 300 second WF₆₅ soak; another soak process may include a20 second SiH₄ followed by a 30 second WF₆ soak; another soak processmay include a 20 second SiH₄ followed by a 100 second WF₆ soak; andanother soak process may include and 20 second B₂H₆ followed by a 200second WF₆ soak.

In one example a metal deposition process comprises a diborane soak, aTaF₅ soak, and the 40 cycles of SiH₄/TaF₅. In another example a metaldeposition process comprises a diborane soak, a WF₆ soak, and the 40cycles of Si₂H₆/TaF₅. A soak layer may also be used between a pluralityof metal nitride 430 and metal layer 440 cycles to improve layerformation or when deposition compounds are changed. For example, a metallayer 440 as described herein may be deposited by 20 cycles ofdiborane/TaF₅, a SiH₄ soak for 60 seconds, and then 40 to 200 cycles ofSiH₄/TaF₅.

A purge gas pulse may be used after each soak precursor introduced intothe process chamber prior to introduction of a second soak precursor ora first precursor for an atomic layer deposition process. Additionally,each soak precursor may be introduced into the process chamber with acarrier gas. Suitable purge gases and/or carrier gases include helium,argon, hydrogen, nitrogen, forming gas, or combinations thereof.

Soak processes may be performed under the following conditions includingsupplying a metal tantalum precursor at a rate between about 1 sccm andabout 1,000 sccm, such as between about 25 sccm and about 500 sccm,and/or supplying the reductant at a rate between about 1 sccm and about1,000 sccm, such as between about 25 sccm and about 500 sccm, supplyinga carrier gas at a flow rate between about 100 sccm and about 1,000sccm, such as between about 100 sccm and about 700 sccm, maintaining thechamber pressure less than about 120 Torr, such as between about 1 Torrand about 50 Torr, for example, between about 1 Torr and about 5 Torr,and maintaining the heater temperature between about 100° C. and about600° C., such as between 175° C. and about 350° C., for example 300° C.

It is believed that the exposure of the substrate surface to the soakprocessing gases provides a better surface for chemisorbtion of metalprecursors, including faster cycle times. The use of soak processinggases, such as ammonia with its respective amines, catalyze thereduction reaction of metal from metal containing precursors, such asTaF₅. The addition of a soak layer has been observed to decreaseresistivity and improve uniformity in subsequent deposition layers atincreasing exposure times to reductants.

Metal Nitride Barrier Layer

Referring to FIG. 4B, the metal nitride barrier layer 430 is conformallydeposited on the floor 418 as well as the side walls 416 of the featuredefinition 414. The metal nitride barrier layer 430 is formed byproviding one or more pulses of a metal containing compound and one ormore pulses of a nitrogen containing compound.

In one example, the barrier layer comprises tantalum nitride and isformed by providing one or more pulses of a tantalum metal containingcompound at a flow rate between about 100 sccm and about 1,000 sccm fora time period of less than about 1 second and one or more pulses of anitrogen containing compound at a flow rate between about 100 sccm andabout 1,000 sccm for a time period of less than about 1 second to areaction zone having a substrate disposed therein. The metal nitridebarrier layer 430 process is performed under conditions suitable forreacting the compounds to produce a TaN layer in the featuredefinitions. The metal nitride barrier layer 430 process may be a plasmaenhanced process.

Exemplary tantalum metal containing compounds include organometallictantalum containing compounds, for example,t-butylimino-tris(diethylamino)tantalum (TBTDET),pentakis(ethylmethylamino)tantalum (PEMAT),pentakis(dimethylamino)tantalum (PDMAT), pentakis(diethylamino)tantalum(PDEAT), t-butylimino-tris(ethylmethylamino)tantalum (TBTMET),t-butylimino-tris(dimethylamino)tantalum (TBTDMT),bis(cyclopentadienyl)tantalum trihydride ((Cp)₂TaH₃),bis(methylcyclopentadienyl)tantalum trihydride ((CpMe)₂TaH₃), tantalumhydride (Cp)₂TaH₃, tantalum pentafluoride (TaF₅), tantalum pentachloride(TaCl₅), tantalum pentabromide (TaBr₅), tantalum pentaiodide (Tal₅), andcombinations thereof.

Exemplary nitrogen containing compounds include activated-dinitrogen,ammonia, hydrazine, methylhydrazine, dimethylhydrazine,t-butylhydrazine, phenylhydrazine, azoisobutane, ethylazide,tert-butylamine, allylamine, derivatives thereof, and combinationsthereof. Also, nitrogen containing compounds may be activated with aplasma, for example, a remote plasma nitridation (RPN) process.

It is to be understood that these compounds or any other compound notlisted above may be a solid, liquid, or gas at room temperature. Forexample, PDMAT is a solid at room temperature and TBTDET is a liquid atroom temperature. Accordingly, the non-gas phase precursors aresubjected to a sublimation or vaporization step, which are both wellknown in the art, prior to introduction into the processing chamber. Acarrier gas, such as argon, helium, nitrogen, hydrogen, or a mixturethereof, may also be used to help deliver the compound into theprocessing chamber.

Each pulse is performed sequentially, and is accompanied by a separateflow of purge gas at a rate between about 200 sccm and about 1,000 sccm.The separate flow of purge gas (purge or purge pulse) may be pulsedbetween each pulse of the reactive compounds or the separate flow ofpurge gas may be introduced continuously throughout the depositionprocess. The separate flow of purge gas, whether pulsed or continuous,serves to remove any excess reactants from the reaction zone to preventunwanted gas phase reactions of the reactive compounds, and also servesto remove any reaction by-products from the processing chamber. Inaddition to these services, the continuous separate flow of purge gashelps deliver the pulses of reactive compounds to the substrate surfacesimilar to a carrier gas.

The durations for each pulse/dose are variable and may be adjusted toaccommodate, for example, the volume capacity of the processing chamberas well as the capabilities of a vacuum system coupled thereto.Additionally, the dose time of a compound may vary according to the flowrate of the compound, the pressure of the compound, the temperature ofthe compound, the type of dosing valve, the type of control systememployed, as well as the ability of the compound to adsorb onto thesubstrate surface. Dose times may also vary based upon the type of layerbeing formed and the geometry of the device being formed.

Typically, the duration for each pulse/dose or “dose time” is typicallyless than about 1 second. In general, a dose time should be long enoughto provide a volume of compound sufficient to adsorb/chemisorb onto thesurface of the substrate and form a layer of the compound thereon.

In a particular embodiment, a TaN barrier layer is formed by cyclicallyintroducing PDMAT and ammonia to the substrate surface. To initiate thecyclical deposition of the TaN layer, a carrier gas such as argon isintroduced into the processing chamber 200 to stabilize the pressure andtemperature therein. The carrier gas is allowed to flow continuouslyduring the deposition process such that only the argon flows betweenpulses of each compound. A first pulse of PDMAT is provided from the gassource 238 at a flow rate between about between about 100 sccm and about400 sccm, with a pulse time of about 0.6 seconds or less after thechamber temperature and pressure have been stabilized at about 200° C.to about 300° C. and about 1 Torr to about 5 Torr. A pulse of ammonia isthen provided from the gas source 239 at a flow rate between about 200sccm and about 600 sccm, with a pulse time of about 0.6 seconds or less.

A pause between pulses of PDMAT and ammonia is about 1.0 second or less,preferably about 0.5 seconds or less, more preferably about 0.1 secondsor less. In various aspects, a reduction in time between pulses at leastprovides higher throughput. As a result, a pause after the pulse ofammonia is also about 1.0 second or less, about 0.5 seconds or less, orabout 0.1 seconds or less. Argon gas flowing between about 100 sccm andabout 1,000 sccm, such as between about 100 sccm and about 400 sccm, iscontinuously provided from the gas source 240 through each valve 242. Inone aspect, a pulse of PDMAT may still be in the chamber when a pulse ofammonia enters. In general, the duration of the carrier gas and/or pumpevacuation should be long enough to prevent the pulses of PDMAT andammonia from mixing together in the reaction zone.

The heater temperature is maintained between about 100° C. and about300° C. at a chamber pressure between about 1.0 and about 5.0 Torr. Eachcycle consisting of a pulse of PDMAT, pause, pulse of ammonia, and pauseprovides a tantalum nitride layer having a thickness between about 0.3 Åand about 1.0 Å per cycle. The alternating sequence may be repeateduntil the desired thickness is achieved, which may be less than about 20Å, such as about 10 Å. Accordingly, the deposition method may requirebetween 10 and 70 cycles, and has been observed to be more typicallybetween 20 and 30 cycles for a desired thickness less than about 20 Å,such as about 10 Å.

Tantalum nitride layer deposited by the process may have a layercomposition of tantalum to nitrogen ratio from about 1:1.92 to about 1:1to about 3:1.

The tantalum nitride deposition process may be performed under thefollowing deposition conditions including supplying the tantalumprecursor at a rate between about 1 sccm and about 100 sccm, such asbetween about 5 sccm and about 50 sccm, supplying the nitrogencontaining reductant at a rate between about 1 sccm and about 100 sccm,such as between about 5 sccm and about 50 sccm, supplying a carrier gasat a flow rate between about 100 sccm and about 1,000 sccm, such asbetween about 100 sccm and about 700 sccm, maintaining the chamberpressure less than about 120 Torr, such as between about 1 Torr andabout 50 Torr, for example, between about 1 Torr and about 5 Torr, andmaintaining the deposition temperature between about 100° C. and about400° C., such as between 175° C. and about 350° C., for example 300° C.ALD deposition of metal and metal nitride layer are more furtherdescribed in U.S. patent application Ser. No. 10/281,079, filed on Oct.25, 2002, which is incorporated by reference to the extent notinconsistent with the claim aspects and disclosure herein.

Metal Barrier Layer

Referring to FIG. 4C, the metal barrier layer 440 is conformallydeposited on the floor 418 as well as the side walls 416 of the featuredefinition 414 or on the metal nitride barrier layer 430 describedherein. The metal nitride barrier layer 430 is formed by providing oneor more pulses of a metal containing compound and one or more pulses ofa reductant. Each pulse is adjusted to provide a desirable composition,thickness, density, and step coverage of the metal barrier layer 440.The metal barrier layer 440 broadly includes metals, such as tantalum(Ta) and derivative metals besides tantalum nitride, such as tantalumsilicide (TaSi), tantalum boride (TaB), tantalum boronitride (TaBN), andtantalum silicon nitride (TaSiN). The metal barrier layer 440 processmay be a plasma enhanced process.

In one example, the barrier layer comprises tantalum and is formed byproviding one or more pulses of a tantalum containing compound at a flowrate between about 100 sccm and about 1,000 sccm for a time period ofless than about 5 seconds and one or more pulses of a reductant at aflow rate between about 100 sccm and about 1,000 sccm for a time periodof less than about 5 seconds to a reaction zone having a substratedisposed therein. The metal barrier layer 440 process is performed underconditions suitable for reacting the compounds to produce a Ta layer, orTa derivative layer, in the feature definitions.

Exemplary tantalum metal containing compounds include organometallictantalum containing compounds, for example,t-butylimino-tris(diethylamino)tantalum (TBTDET),pentakis(ethylmethylamino)tantalum (PEMAT),pentakis(dimethylamino)tantalum (PDMAT), pentakis(diethylamino)tantalum(PDEAT), t-butylimino-tris(ethylmethylamino)tantalum (TBTMET),t-butylimino-tris(dimethylamino)tantalum (TBTDMT),bis(cyclopentadienyl)tantalum trihydride ((Cp)₂TaH₃),bis(methylcyclopentadienyl)tantalum trihydride ((CpMe)₂TaH₃),derivatives thereof; and combinations thereof. Preferred metalcontaining compounds also include inorganometallic tantalum containingcompounds, for example, tantalum pentafluoride (TaF₅), tantalumpentachloride (TaCl₅), tantalum pentabromide (TaBr₅), tantalumpentaiodide (Tal₅), and combinations thereof. The metal containingprecursor for the metal barrier layer 440 may be the same precursor forthe metal nitride barrier layer 430.

Exemplary reductants include nitrogen free reductants includinghydrogen, borane and borane derivatives such as diborane (B₂H₆),triborane, tetraborane, pentaborane, hexaborane, heptaborane,octaborane, nanoborane, decaborane, alkylboranes (e.g., Et₃B), andcombinations thereof, silane and silane derivatives such astetrachlorosilane (SiCl₄), disilane (Si₂H₆), hexachlorodisilane (Si₂Cl₆)or dichlorosilane (SiCl₂H₂). Alternatively, the reductants may alsoinclude nitrogen containing compounds selected from the group ofammonia, hydrazine, methylhydrazine, dimethylhydrazine,t-butylhydrazine, phenylhydrazine, azoisobutane, ethylazide, derivativesthereof, and combinations thereof. A carrier gas, such as argon, helium,nitrogen, hydrogen, or a mixture thereof, may also be used to helpdeliver the compound into the processing chamber.

Each pulse is performed sequentially, and is accompanied by a separateflow of purge gas at a rate between about 200 sccm and about 1,000 sccm.The separate flow of purge gas may be pulsed between each pulse of thereactive compounds or the separate flow of purge gas may be introducedcontinuously throughout the deposition process.

The durations for each pulse/dose are variable and may be adjusted toaccommodate, for example, the volume capacity of the processing chamberas well as the capabilities of a vacuum system coupled thereto.Additionally, the dose time of a compound may vary according to the flowrate of the compound, the pressure of the compound, the temperature ofthe compound, the type of dosing valve, the type of control systememployed, as well as the ability of the compound to adsorb onto thesubstrate surface. Dose times may also vary based upon the type of layerbeing formed and the geometry of the device being formed.

Typically, the duration for each pulse/dose or “dose time” is typicallyless than about 1 second. However, a dose time can range frommicroseconds to milliseconds to seconds, and even to minutes. Ingeneral, a dose time should be long enough to provide a volume ofcompound sufficient to adsorb/chemisorb onto the entire surface of thesubstrate and form a layer of the compound thereon.

In a particular embodiment, a tantalum boride or tantalum silicidebarrier layer is formed by cyclically introducing tantalum pentafluorideand diborane or silane or disilane to the substrate surface. To initiatethe cyclical deposition of the Ta layer, a carrier gas such as argon isintroduced into the processing chamber 200 to stabilize the pressure andtemperature therein. The carrier gas is allowed to flow continuouslyduring the deposition process such that only the argon flows betweenpulses of each compound. One example of a first pulse of TaF₅ providedto the chamber from the gas source 238 includes a flow rate betweenabout 100 sccm and about 400 sccm, with a pulse time of less than about5 seconds, for example about 0.6 seconds or less, after the chambertemperature and pressure have been stabilized between about 200° C. andabout 600° C., for example between about 300° C. and about 350° C., andabout 1 Torr to about 5 Torr. A pulse of diborane or silane or disilaneis then provided from the gas source 239 at a flow rate between about200 sccm and about 600 sccm, with a pulse time of less than about 5seconds, preferably less than about 1 second for example about 0.6seconds or less. The heater temperature is maintained between about 100°C. and about 650° C. for a chamber pressure between about 1 Torr andabout 5 Torr.

A pause between pulses of TaF₅ and diborane or silane may be less thanabout 5 seconds, such as less than about 1 second, preferably about 0.5seconds or less, more preferably about 0.1 seconds or less. In variousaspects, a reduction in time between pulses at least provides higherthroughput. As a result, a pause after the pulse of diborane or silaneor disilane is also less than about 5 seconds, such as less than about 1second, preferably about 0.5 seconds or less, or about 0.1 seconds orless. Argon gas flowing between about 100 sccm and about 1,000 sccm,such as between about 100 sccm and about 400 sccm, is continuouslyprovided from the gas source 240 through each valve 242A, 242B. In oneaspect, a pulse of TaF₅ may still be in the chamber when a pulse ofdiborane or silane or disilane enters. In general, the duration of thecarrier gas and/or pump evacuation should be long enough to prevent thepulses of TaF₅ and diborane or silane from mixing together in thereaction zone.

Each cycle consisting of a pulse of TaF₅, pause, pulse of diborane orsilane or disilane, and pause provides a tantalum layer having athickness of about 5

A or less, such as between about 3 Å and about 4 Å, per cycle. Thealternating sequence may be repeated until the desired thickness isachieved, which is less than about 50 Å, such as about 10 Å.Accordingly, the deposition method requires between 2 cycles and 70cycles, more typically between 20 cycles and 30 cycles. A process asdescribed may deposit a tantalum layer having a film resistivity betweenabout 180 micro-ohms-centimeter (μΩ-cm), with a silicon content of about30 atomic or weight percent or less, and a fluorine content of less thanabout 1 atomic or weight percent.

The process described herein also contemplates depositing a ternarycompound such as tantalum boronitride or tantalum silicon nitride. Theprocess described herein may be adapted to include a pulse of a nitrogencontaining reductant, such as ammonia either preceding or subsequent toa diborane or silane pulse. In one embodiment, each cycle consists of apulse of a tantalum containing compound, a pause, a pulse of a boroncontaining compound, such as borane, or a silane compound, such assilane or disilane, a pause, a pulse of a nitrogen containing compound,and a pause. Each pulse is performed sequentially, and is accompanied bya separate flow of carrier gas at the same process conditions describedabove. The separate flow of purge gas may be pulsed between each pulseof reactive compound or the separate flow of carrier gas may beintroduced continuously throughout the deposition process.

Alternatively, one or more reductants may be used in the deposition ofmetal barrier layer 440 to form one or more binary compounds. Thereductants may be alternated or substituted during cyclical deposition.For example, in a substitution deposition technique, a metal barrierlayer 440 is first deposited by 20 cycles of diborane/TaF₅ and then 40cycles of SiH₄/TaF₅. In an alternating precursor technique, a metalbarrier layer 440 may be deposited by a cycle of diborane/TaF₅ and thena cycle of SiH₄/TaF₅, and then repeating the process.

Prior to the deposition of barrier metal on top of metal nitride, themetal nitride surface may need to be activated to initial metal barriergrowth by ALD by a soak process described herein. For example, a soakprocess for depositing an ALD Ta(Si) on an ALD TaN can be performed by atwo step soak process. The two-step process includes a reductant soak ofB₂H₆ between about 0.1 seconds and about 60 seconds followed by aprecursor soak of WF₆ between about 0.1 seconds and about 60 seconds toconvert the TaN surface to be fluorine terminated. This soak process maybe further performed to include a reductant exposure to a secondreductant of SiH₄ (or disilane, Si₂H₆) between about 0.1 seconds andabout 10 seconds with a pressure between about 0.01 Torr and about 100Torr to transfer the surface to be silicon terminated so that thesurface is ready to react with TaF₅ to form a tantalum metal barrierlayer. Alternatively, ALD Ta growth can be performed without the SiH₄(or disilane, Si₂H₆) soak step, which presence of silane can result inCuSi formation by the reaction of SiH₄ (or disilane, Si₂H₆) with Cumetal line underneath a via. ALD W layer formed by the tungsten soakprocess may be terminated by SiH₄ (or disilane, Si₂H₆) soak, which canbe a good Cu wetting layer to interface between ALD TaN and Cu.

The tantalum deposition process may be performed under the followingdeposition conditions including supplying the tantalum precursor at arate between about 1 sccm and about 100 sccm, such as between about 5sccm and about 50 sccm, supplying the nitrogen free reductant at a ratebetween about 1 sccm and about 100 sccm, such as between about 5 sccmand about 50 sccm, supplying a carrier gas at a flow rate between about100 sccm and about 1,000 sccm, such as between about 100 sccm and about700 sccm, maintaining the chamber pressure less than about 120 Torr,such as between about 1 Torr and about 50 Torr, for example, betweenabout 1 Torr and about 5 Torr, and maintaining the depositiontemperature between about 100° C. and about 400° C., such as between175° C. and about 350° C., for example 300° C.

Post-Deposition Techniques

The metal nitride layer 430 and/or metal layer 440 may be exposed to areducing plasma to remove contaminants, such as halides, from thesubstrate surface. The plasma treatment may be performed in the samechamber used to deposit the barrier layers 430, 440. The plasmatreatment may be performed after the deposition of the barrier layers430, 440 or after each pulse or pulse cycle for depositing the metal ormetal nitride layers. The plasma treatment generally includes providingan inert gas including helium, argon, neon, xenon, krypton, orcombinations thereof, of which helium is preferred, and/or a reducinggas including hydrogen, ammonia, a reductant as described herein for asoak process, and combinations thereof, to a processing chamber. Thereducing plasma may be specified for each barrier layer 430, 440, suchas hydrogen gas for metal barrier layer 440 and ammonia for metalnitride barrier layer 430. The hydrogen plasma may be a remote plasmatransferred into the processing chamber for treated the substrate.

One example of a possible gas treatment process includes introducing areducing gas, for example, hydrogen, and optionally an inert gas, intothe processing chamber at a total flow rate between about 500 sccm andabout 3000 sccm, such as between about 1,000 sccm and about 2500 sccm ofhydrogen, and generating a plasma in the processing chamber using apower density ranging between about 0.03 W/cm² and about 3.2 W/cm²,which is a RF power level of between about 10 W and about 1,000 W for a200 mm substrate. The RF power can be provided at a high frequency suchas between 13 MHz and 14 MHz. The RF power can be provided continuouslyor in short duration cycles wherein the power is on at the stated levelsfor cycles less than about 200 Hz and the on cycles total between about10% and about 30% of the total duty cycle. Alternatively, the RF powermay also be provided at low frequencies, such as 356 kHz, for plasmatreating the depositing silicon carbide layer. Alternatively microwaveand remote plasma sources may be used to generate a plasma as analternative to RF power applications describe herein.

For the example hydrogen plasma process, the processing chamber may bemaintained at a chamber pressure of between about 10 milliTorr and about12 Torr, the substrate may be maintained at a temperature between about200° C. and about 450° C., during the plasma treatment. The examplehydrogen plasma treatment may be performed between about 10 seconds andabout 100 seconds, with a plasma treatment between about 40 seconds andabout 60 seconds preferably used. The processing gas may be introducedinto the chamber by a gas distributor positioned between about 50 milsand about 600 mils from the substrate surface. However, it should benoted that the respective parameters may be modified to perform theplasma processes in various chambers and for different substrate sizes,such as 300 mm substrates.

An anneal technique may also be performed after the deposition ofindividual layers including the metal nitride barrier layer 430 and themetal barrier layer 440. The anneal process may be performed incombination with the reducing plasma technique herein. For example,deposited layers 430 and/or 440, may be exposed to an annealing processof about 380° C. for about 1 hour in a nitrogen atmosphere.

The anneal technique may also be performed after the deposition of ananneal process. For example, the ALD metal nitride layer 430/ALD metalbarrier 440/Cu seed 450 stack film can be annealed at temperaturebetween about 50 to about 450° C. for about 1 sec to about 600 sec tostabilize ALD metal/Cu seed interface, which can further prevent Cuagglomeration even the stack film is exposed to air prior to ECP copperfill.

Additional Layer Deposition

Alternatively, the metal layer 440 may be enhanced by the deposition ofa metal material deposited by another method. For example, an alphaphase tantalum (α-Ta) layer having a thickness of about 20 Å or less,such as about 10 Å, may be deposited over at least a portion of thepreviously deposited barrier layers 430, 440. The α-Ta layer may bedeposited using conventional techniques, such as PVD and CVD, or evenanother ALFD process. For example, the bilayer stack may include a TaNportion deposited by cyclical layer deposition described above, a Taportion deposited by cyclical layer deposition described above, and anα-Ta portion deposited by high density plasma physical vapor deposition(HDP-PVD).

To further illustrate, the α-Ta portion of the stack may be depositedusing an ionized metal plasma (IMP) chamber, such as a Vectra™ chamber,available from Applied Materials, Inc. of Santa Clara, Calif. The IMPchamber includes a target, coil, and biased substrate support member,and may also be integrated into an Endura™ platform, also available fromApplied Materials, Inc. A power between about 0.5 kW and about 5 kW isapplied to the target, and a power between about 0.5 kW and 3 kW isapplied to the coil. A power between about 200 W and about 500 W at afrequency of about 13.56 MHz is also applied to the substrate supportmember to bias the substrate. Argon is flowed into the chamber at a rateof about 35 sccm to about 85 sccm, and nitrogen may be added to thechamber at a rate of about 5 sccm to about 100 sccm. The pressure of thechamber is typically between about 5 milliTorr to about 100 milliTorr,while the temperature of the chamber is between about 20° C. and about300° C.

Metal Deposition

Referring to FIG. 4D, the seed layer 450 may be deposited using highdensity plasma physical vapor deposition (HDP-PVD) to enable goodconformal coverage. One example of a HDP-PVD chamber is the Self-IonizedPlasma SIP™ chamber, available from Applied Materials, Inc. of SantaClara, Calif., which may be integrated into an Endura™ platform,available from Applied Materials, Inc. Of course, other techniques, suchas physical vapor deposition, chemical vapor deposition, atomic layerdeposition, electroless plating, electroplating, or combinationsthereof, may be used.

A typical SIP™ chamber includes a target, coil, and biased substratesupport member. To form the copper seed layer, a power between about 0.5kW and about 5 kW is applied to the target, and a power between about0.5 kW and 3 kW is applied to the coil. A power between about 200 andabout 500 W at a frequency of about 13.56 MHz is applied to bias thesubstrate. Argon is flowed into the chamber at a rate of about 35 sccmto about 85 sccm, and nitrogen may be added to the chamber at a rate ofabout 5 sccm to about 100 sccm. The pressure of the chamber is typicallybetween about 5 milliTorr to about 100 milliTorr.

Alternatively, a seed layer 450 containing a copper alloy may bedeposited by any suitable technique such as physical vapor deposition,chemical vapor deposition, electroless deposition, or a combination oftechniques. Preferably, the copper alloy seed layer 450 containsaluminum and is deposited using a PVD technique described above. Duringdeposition, the process chamber is maintained at a pressure betweenabout 0.1 milliTorr and about 10 milliTorr. The target includes copperand between about 2 and about 10 atomic weight percent of aluminum. Thetarget may be DC-biased at a power between about 5 kW and about 100 kW.The pedestal may be RF-biased at a power between about 10 W and about1,000 W. The copper alloy seed layer 450 is deposited to a thickness ofat least about 5 Å, and between about 5 Å and about 500 Å.

The metal layer 460 is preferably copper and is deposited using CVD,PVD, electroplating, or electroless techniques. Preferably, the copperlayer 460 is formed within an electroplating cell, such as the ELECTRA®Cu ECP system, available from Applied Materials, Inc., of Santa Clara,Calif. The ELECTRA® Cu ECP system may also be integrated into an ENDURA®platform also available from Applied Materials, Inc.

A copper electrolyte solution and copper electroplating technique isdescribed in commonly assigned U.S. Pat. No. 6,113,771, entitled“Electro-deposition Chemistry”, which is incorporated herein byreference to the extent not inconsistent with the claimed aspects anddisclosure herein. Typically, the electroplating bath has a copperconcentration greater than about 0.7 M, a copper sulfate concentrationof about 0.85, and a pH of about 1.75. The electroplating bath may alsocontain various additives as is well known in the art. The temperatureof the bath is between about 15° C. and about 25° C. The bias is betweenabout −15 volts to about 15 volts. In one aspect, the positive biasranges from about 0.1 volts to about 10 volts and the negatives biasranges from about −0.1 to about −10 volts.

Optionally, an anneal treatment may be performed following the metallayer 460 deposition whereby the wafer is subjected to a temperaturebetween about 100° C. and about 500° C., for example, about 475° C., forabout 10 minutes to about 1 hour, preferably about 30 minutes. Twoexamples of anneal process are exposure to a nitrogen atmosphere for 30minutes at 475° C. and exposure to a nitrogen atmosphere for 1 hour at380° C. A carrier/purge gas such as helium, argon, hydrogen, nitrogen,or a mixture thereof is introduced at a rate of about 100 sccm to about10,000 sccm. The chamber pressure is maintained between about 2 Torr andabout 10 Torr. Optionally, a RF power may be applied between about 200 Wto about 1,000 W at a frequency of about 13.56 MHz. Preferable substratespacing is between about 300 mils and about 800 mils.

Following deposition, the top portion of the resulting structure may beplanarized. A chemical mechanical polishing (CMP) apparatus may be used,such as the Mirra™ System available from Applied Materials, Santa Clara,Calif., for example. Optionally, the intermediate surfaces of thestructure may be planarized between the depositions of the subsequentlayers described above.

The following example is intended to provide a non-limiting illustrationof one embodiment of the present invention.

EXAMPLES

A tantalum (Ta) layer was deposited on a TaN layer by using a multi-stepcyclical deposition process as follows with a soak process.

The tantalum nitride layer was formed by a process comprising flowingTaF₅, SiH₄ and NH₃ or TaF₅, NH₃ and SiH₄. For example, the tantalumnitride layer may be deposited at 325° C. by depositing about 5 Å TaN bya PDMAT/NH₃ process, then a ten cycle process of NH₃ for about 3seconds, SiH₄ for about 1 second, TaF₅ for about 2 seconds, a SiH₄ soak,and then a cycle of SiH₄ for about 1 second and TaF₅ for about 1 second.

The soak process forms an initial layer of tungsten by one or multiplecycles of diborane (B₂H₆) and tungsten fluoride (WF₆) to preventexcessive silane (or disilane) exposures. The tungsten layer is exposedto small dose of silane (or disilane) exposures to convert the surfaceto be SiH terminated such that the surface is ready to react with TaF₅to initiate ALD Ta growth. For example, the soak process may comprisediborane (5% in argon, 5 Torr) exposure for between about 3 seconds andabout 10 seconds, followed by a tungsten hexafluoride soak for about 1second. Alternatively, a soak process to form an initial layer ofTaSi_(x)N_(y) was formed using ammonia exposure for between about 5seconds and about 20 seconds, a purge process for 5 seconds, followed bya tungsten hexafluoride soak for about 3 seconds.

The tantalum (Ta) layer was then deposited using a multi-step cyclicaldeposition process as follows. The tantalum material was deposited witha multiple cycles comprising 2 second silane (SiH₄) or disilane, 1second purge of argon, 4 seconds of and TaF₅ in helium carrier gas, anda 1 second purge of argon before repeating the cycle. Alternatively, aninitial layer of tantalum was deposited by 20 cycles of diborane (B₂H₆)and tantalum pentafluoride (TaF₅), a soak layer of silane was depositedfor 60 seconds, and remaining tantalum material was deposited for 200cycles of silane (SiH₄) and TaF₅. The substrate was than annealed forone hour at 380° C. in a nitrogen environment.

According to the processes described herein, a tantalum (Ta) layer wasdeposited using a multi-step cyclical deposition process by cycles ofsilane (SiH₄) and TaF₅ at a deposition rate of between about 1 Å andabout 5 Å to produce a film having a film resistivity of about 180 μΩ-cmwith about 30 atomic % Si and less than 1 atomic % F, which exhibitedgood copper adhesion and wetting verified after 470° C. anneal.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for forming metal interconnect structures on a substratesurface, comprising: exposing a substrate to tungsten hexafluoride and areducing gas to form an initiation layer on the substrate during a soakprocess; depositing a barrier layer comprising tungsten nitride on thesubstrate during a first atomic layer deposition process; exposing thebarrier layer to a first processing gas comprising silane or diboraneprior to depositing a tungsten-containing layer; depositing thetungsten-containing layer on the barrier layer during a second atomiclayer deposition process; exposing the tungsten-containing layer to asecond processing gas comprising silane or diborane prior to depositinga bulk metal layer comprising tungsten; and depositing the bulk metallayer comprising tungsten on the substrate during a chemical vapordeposition process.
 2. The method of claim 1, wherein the firstprocessing gas or the second processing gas further comprises hydrogengas.
 3. The method of claim 1, wherein the substrate is exposed to thefirst processing gas or the second processing gas for a time periodwithin a range from about 5 seconds to about 330 seconds.
 4. The methodof claim 1, wherein the reducing gas comprises a reductant selected fromthe group consisting of silane, diborane, hydrogen, plasmas thereof,derivatives thereof, and combinations thereof.
 5. The method of claim 4,wherein the reducing gas comprises hydrogen and silane.
 6. The method ofclaim 4, wherein the reducing gas comprises hydrogen and diborane. 7.The method of claim 4, wherein the soak process comprises exposing thesubstrate to the tungsten hexafluoride and subsequently exposing thesubstrate to the reducing gas.
 8. The method of claim 1, wherein thetungsten-containing layer comprises a material selected from the groupconsisting of metallic tungsten, tungsten boride, tungsten silicide,alloys thereof, and combinations thereof.
 9. A method for forming metalinterconnect structures on a substrate surface, comprising: exposing asubstrate to tungsten hexafluoride and a reducing gas to form aninitiation layer on the substrate during a soak process; depositing abarrier layer comprising tungsten nitride on the substrate during afirst atomic layer deposition process; depositing a tungsten-containinglayer on the barrier layer during a second atomic layer depositionprocess; and depositing a bulk metal layer comprising tungsten on thesubstrate during a chemical vapor deposition process.
 10. The method ofclaim 9, wherein the reducing gas comprises a reductant selected fromthe group consisting of silane, diborane, hydrogen, plasmas thereof,derivatives thereof, and combinations thereof.
 11. The method of claim10, wherein the reducing gas comprises hydrogen and silane.
 12. Themethod of claim 10, wherein the reducing gas comprises hydrogen anddiborane.
 13. The method of claim 10, wherein the soak process comprisesexposing the substrate to the tungsten hexafluoride and subsequentlyexposing the substrate to the reducing gas.
 14. The method of claim 9,wherein the tungsten-containing layer comprises a material selected fromthe group consisting of metallic tungsten, tungsten boride, tungstensilicide, alloys thereof, and combinations thereof.
 15. The method ofclaim 9, wherein another metal layer is deposited on the substratesubsequent to the tungsten-containing layer and prior to the bulk metallayer comprising tungsten.
 16. The method of claim 9, wherein thebarrier layer is exposed to a processing gas comprising silane ordiborane prior to depositing the tungsten-containing layer.
 17. Themethod of claim 16, wherein the processing gas further compriseshydrogen gas.
 18. The method of claim 16, wherein the barrier layer isexposed to the processing gas for a time period within a range fromabout 5 seconds to about 330 seconds.
 19. The method of claim 9, whereinthe tungsten-containing layer is exposed to a processing gas comprisingsilane or diborane prior to depositing the bulk metal layer.
 20. Themethod of claim 19, wherein the processing gas further compriseshydrogen gas.
 21. The method of claim 19, wherein thetungsten-containing layer is exposed to the processing gas for a timeperiod within a range from about 5 seconds to about 330 seconds.
 22. Amethod for forming metal interconnect structures on a substrate surface,comprising: exposing a substrate to tungsten hexafluoride and a reducinggas to form an initiation layer on the substrate during a soak process;depositing a barrier layer comprising tungsten nitride on the substrateduring a first atomic layer deposition process; depositing aruthenium-containing layer on the barrier layer during a second atomiclayer deposition process; and depositing a bulk metal layer on thesubstrate.
 23. The method of claim 22, wherein the reducing gascomprises a reductant selected from the group consisting of silane,diborane, hydrogen, plasmas thereof, derivatives thereof, andcombinations thereof.
 24. The method of claim 23, wherein the reducinggas comprises hydrogen and silane.
 25. The method of claim 23, whereinthe reducing gas comprises hydrogen and diborane.
 26. The method ofclaim 23, wherein the soak process comprises exposing the substrate tothe tungsten hexafluoride and subsequently exposing the substrate to thereducing gas.
 27. The method of claim 22, wherein theruthenium-containing layer comprises a material selected from the groupconsisting of metallic ruthenium, ruthenium boride, ruthenium silicide,alloys thereof, and combinations thereof.
 28. The method of claim 27,wherein another metal layer is deposited on the substrate subsequent tothe ruthenium-containing layer and prior to the bulk metal layer. 29.The method of claim 28, wherein the other metal layer comprises copperor a copper alloy.
 30. The method of claim 29, wherein the other metallayer is deposited by a physical vapor deposition process, anelectroplating process, or an electroless plating process.
 31. Themethod of claim 22, wherein the barrier layer is exposed to a processinggas comprising silane or diborane prior to depositing theruthenium-containing layer.
 32. The method of claim 31, wherein theprocessing gas further comprises hydrogen gas.
 33. The method of claim31, wherein the barrier layer is exposed to the processing gas for atime period within a range from about 5 seconds to about 330 seconds.34. The method of claim 22, wherein the ruthenium-containing layer isexposed to a processing gas comprising silane or diborane prior todepositing the bulk metal layer.
 35. The method of claim 34, wherein theprocessing gas further comprises hydrogen gas.
 36. The method of claim34, wherein the ruthenium-containing layer is exposed to the processinggas for a time period within a range from about 5 seconds to about 330seconds.
 37. The method of claim 30, wherein the bulk metal layercomprises copper or a copper alloy.
 38. The method of claim 37, whereinthe bulk metal layer is deposited by a physical vapor depositionprocess, an electroplating process, or an electroless plating process.39. The method of claim 22, wherein the bulk metal layer comprisescopper or a copper alloy.
 40. The method of claim 39, wherein the bulkmetal layer is deposited by a physical vapor deposition process, anelectroplating process, or an electroless plating process.
 41. Themethod of claim 22, wherein the bulk metal layer comprises tungsten or atungsten alloy.
 42. The method of claim 41, wherein the bulk metal layeris deposited by a physical vapor deposition process or a chemical vapordeposition process.